1. Field of the Invention
This invention relates to a method of making a fiber-loaded polymeric sheet particularly adapted for use in polymeric power transmission belts and to such belts utilizing same.
2. Prior Art Statement
It is known in the art to provide a flowable polymeric composition which has a plurality of discrete elongate fibers therein which are mixed together in a suitable mixing device, such as a Banbury mill, or the like, to define a fiber-loaded polymeric mass. The fiber-loaded mass is then processed through a suitable device, such as a cooperating pair of calendering rolls, to define a fiber-loaded sheet which has fibers aligned in substantially parallel relation.
However, in using the above techniques with fibers having lengths above approximately 3/16", there is a tendency for such fibers to roll into small balls, i.e., "pill", during mixing. Further, as the quantity of fibers relative to the quantity of polymeric material used to define the polymeric matrix therefor increases, there is a tendency for the entire batch of components being mixed to become hotter and the fiber dispersion to be comparatively poor. The net result is that fiber-loaded polymeric sheets made as described above are usually made with only roughly 20% of the fibers comprising same. In addition, previously used techniques, such as using calendering rolls, result in a maximum of about 50% of the fibers being disposed with their longitudinal axes in parallel relation whereby the above-described techniques have the deficiencies indicated.
It is also known in the art to provide a method of making a fiber-loaded polymeric sheet in a substantially continuous and uninterrupted manner wherein the method comprises the steps of disposing a quantity of discrete elongate fibers as a layer thereof on movable support means therefor which is movable along a rectilinear path and in a substantially horizontal plane, providing a quantity of liquid-containing polymeric material around the fibers during movement of the support means and the fibers, and removing the liquid contained in the liquid-containing polymeric material to define the sheet and as disclosed in U.S. Pat. No. 2,964,441.
It is also known to provide an endless power transmission belt which has at least one part or sheet portion thereof comprised of a polymeric material which has a plurality of elongate reinforcing fibers embedded therein and with the polymeric material serving as a matrix for the fibers. Examples of belts which use elongate reinforcing fibers in at least one part or sheet portion thereof are presented in the following patents, together with a brief comment on each patent:
(1) U.S. Pat. No. 3,416,383 discloses raw-edged belts which have oriented reinforcing fibers in various parts;
(2) U.S. Pat. No. 3,838,605 discloses a banded belt with belt bodies interconnected by a web using fibers;
(3) U.S. Pat. No. 3,839,116 discloses a belt having integral longitudinal ribs and which uses a fabric cover on the ribs and on the outside surface of the belt as well as fibers within the belt body;
(4) U.S. Pat. No. 3,863,515 discloses a belt using cords skewed in opposite directions on opposite sides of the load-carrying cord;
(5) U.S. Pat. No. 3,924,482 discloses a belt having a cover covering the entire belt body;
(6) U.S. Pat. No. 3,987,684 discloses raw-edged belts having centrally disposed load-carrying cords, fibers in various sections, and covers for the inside and outside surfaces thereof;
(7) U.S. Pat. No. 4,027,545 discloses various belts having inside and outside covers and a load-carrying section comprised of reinforcing fibers;
(8) U.S. Pat. No. 4,031,768 discloses various belts, including a belt with a toothed compression section, which use reinforcing fibers; and
(9) U.S. Pat. No. 3,078,205 discloses a so-called synchronous type belt which uses a facing fabric for its belt teeth.
It is an object of this invention to provide an improved method of making a fiber-loaded polymeric sheet in a substantially continuous and uninterrupted manner.
Another object of this invention is to provide an improved endless power transmission belt which employs an improved fiber-loaded sheet of the character mentioned.
Other aspects, embodiments, objects, and advantages of this invention will become apparent from the following specification, claims, and drawings.